Cables and computers are seen inside a data centre at an office in the heart of the financial district in London, Britain May 15, 2017. REUTERS/Dylan Martinez

LONDON (Reuters) - Cyber attackers are regularly trying to attack data networks connected to critical national infrastructure systems around Europe, according to current and former European government sources with knowledge of the issue.

The sources acknowledged that European infrastructure data networks face regular attacks similar to those which the Washington Post newspaper said on Sunday had been launched by Russian government hackers against business systems of U.S. nuclear power and other companies involved in energy production.

One former senior British security official said it was an “article of faith” that Russian government hackers were seeking to penetrate UK critical infrastructure though the official said he could not cite public case studies.

A European security source acknowledged that UK authorities were aware of the latest reports about infrastructure hacking attempts and that British authorities were in regular contact with other governments over the attacks.

UK authorities declined to comment on the extent of any such attempted or successful attacks in Britain or elsewhere in Europe or to discuss what possible security measures governments and infrastructure operators might be taking.

The Washington Post said recent attempted Russian hacking attacks on infrastructure related systems in the United States appeared to be an effort to “assess” such networks.

But there was no evidence that hackers had actually penetrated or disrupted key systems controlling operations at nuclear plants.

The Post cited several U.S. and industry officials saying that this was the first time hackers associated with the Russian government are known to have tried to get into US nuclear power companies.

The newspaper said that in late June the Federal Bureau of Investigations (FBI) and the U.S. Homeland Security Department warned energy companies that unnamed foreign hackers were trying to steal login and password information so they could hack into networks.

U.S. officials have acknowledged that many key computer systems which run critical infrastructure ranging from power grids to transportation networks originally were not built with strong security protection against outside hackers.

Security experts in the U.S. and Europe acknowledge that the development and evolution of security measures to protect critical infrastructure system against outside intruders has often run behind the ability of hackers to invent tools to get inside such systems.